The present invention relates to an improved valve gear train for an internal combustion engine, and more particularly, to a valve deactivator sub-assembly for use therein.
Although the valve deactivator sub-assembly of the present invention may be utilized to introduce some additional lash into the valve train, such that the valves open and close by an amount less than the normal opening and closing, the invention is especially suited for introducing into the valve train sufficient lash (also referred to hereinafter as xe2x80x9clost motionxe2x80x9d), such that the valves no longer open and close at all, and the invention will be described in connection therewith.
Valve deactivators of the general type to which the invention relates are known, especially in connection with internal combustion engines having push rod type valve gear trains in which there is a rocker arm, with one end of the rocker arm engaging the push rod, and the other end engaging the engine poppet valve. Typically, a central portion of the rocker arm is fixed relative to the cylinder head (or other suitable structure) by a fulcrum arrangement as is well know to those skilled in the art, in which the fulcrum normally prevents movement of the central portion of the rocker arm in an xe2x80x9cup and downxe2x80x9d direction. At the same time, the fulcrum permits the rocker arm to engage in cyclical, pivotal movement, in response to the cyclical motion of the push rod, which results from the engagement of the push rod with the lobes of the rotating cam shaft.
There are a number of known valve deactivator sub-assemblies which are operably associated with the fulcrum portion of the rocker arm and which, in the latched condition, restrain the fulcrum portion of the rocker arm to move in its normal cyclical, pivotal movement. However, In an unlatched condition, the valve deactivator sub-assembly permits the fulcrum portion of the rocker arm to engage in xe2x80x9clost motionxe2x80x9d such that the cyclical, pivotal movement of the push rod causes the rocker arm to undergo cyclical, pivotal movement about the end which is in engagement with the engine poppet valve. In other words, the rocker arm merely pivots, but the engine poppet valve does not move and therefore, is in its deactivated condition.
Although the known valve deactivator sub-assemblies of the type referred to above have performed in a generally satisfactory manner, such sub-assemblies do add substantially to the overall cost of the valve gear train, and in many cases also add undesirably to the space taken up by the overall rocker arm installation. In some engine designs, there is simply no room to add a valve deactivator sub-assembly of the type which is associated with the rocker arm fulcrum member.
Typically, in a push rod type of valve gear train, there is some sort of cam follower device having one portion thereof in engagement with the cam lobe on the engine cam shaft, and another portion thereof in engagement with the lower end of the push rod. It is also known for such a cam follower mechanism to include a hydraulic lash compensation element. It is now also known to incorporate a valve deactivator mechanism into the cam follower, thus eliminating the need for adding to the rocker arm assembly the type of expensive, space consuming structure described above.
On a normal internal combustion engine having valve gear train of the push rod type described above, and including some form of valve deactivation capability, it would be typical for less than all of the engine poppet valves to be equipped with the valve deactivation capability. In other words, on an eight cylinder engine, by way of example only, it would be typical to provide valve deactivation capability on both the intake and exhaust valves of four of the eight cylinders, while equipping the intake and exhaust valves of the other four cylinders with conventional roller followers. In such an engine configuration, installation of the proper roller follower at each location within the engine can be a problem because, typically, the valve deactivating roller follower and the conventional roller follower to be used in a particular engine would be the same overall size, shape, and configuration, such that during the engine assembly process, it would be very easy to put a valve deactivating roller follower in a location intended to have a conventional roller follower, or vice-versa.
It is known in valve gear train of the type to which this invention relates to provide some sort of guide member for the roller followers to prevent rotation of the roller followers about their longitudinal axes, in order to maintain the roller followers in their proper rotational orientation relative to the associated cam lobe. In other words, the axis of the roller of the roller follower must remain parallel to the axis of the cam shaft.
Accordingly, it is an object of the present invention to provide an improved valve deactivator sub-assembly, including a guide member, which overcomes the above-described disadvantages of the prior art.
It is a more specific object of the present invention to provide an improved valve deactivator sub-assembly and guide member which will insure that deactivating roller followers are installed only at deactivation follower locations, and that conventional roller followers are installed only at conventional follower locations.
It is another object of the present invention to provide an improved valve deactivator sub-assembly, including a guide member, which accomplishes the above-stated objects, and which also insures that each roller follower is oriented correctly, rotationally, so that, for example, each fluid port in the roller follower is aligned with the correct fluid passage in the engine block.
The above and other objects of the invention are accomplished by the provision of a valve actuation sub-assembly for an internal combustion engine of a type having a valve means for controlling the flow to and from a combustion chamber, and valve gear means operative in response to a cyclical input motion to effect cyclical opening and closing of the valve means. The valve actuation sub-assembly is adapted for attachment relative to an engine block including a cam shaft defining first and second cam profiles operable to provide the cyclical input motion in response to rotation of the cam shaft. The engine block defines first and second follower bores disposed adjacent the first and second cam profiles, respectively. The valve actuation sub-assembly comprises first and second roller followers, to be disposed in the first and second follower bores, respectively, each of the roller followers including a roller for operative engagement with its respective cam profile, an outer body fixed to move axially with its roller, and the outer body including an upper portion projecting out of its respective follower bore. Each roller follower includes an inner body disposed within the outer body, and including a push rod socket, and a push rod in engagement with the socket and operable to transmit the cyclical input motion to the valve gear means. The valve actuation sub-assembly further comprises a follower guide member adapted for attachment to the engine block and defining first and second guide receptacles operable to receive and guide the upper portions of the outer body of the first and second roller followers, respectively.
The improved valve actuation sub-assembly is characterized by the first guide receptacle defining a first internal profile configured to be closely spaced relative to the upper portion of the outer body of the first roller follower. The first internal profile is not capable of receiving the upper portion of the outer body of the second roller follower. The second guide receptacle defines a second internal profile configured to be closely spaced relative to the upper portion of the outer body of the second roller follower. The second internal profile is not capable of receiving the upper portion of the outer body of the first roller follower.
In accordance with a further aspect of the invention, the valve actuation sub-assembly is characterized by the first roller follower comprising a conventional roller follower and the second roller follower comprising a deactivating roller follower. The second roller follower includes a latching arrangement operable between a latched condition, latching the inner body for movement with the outer body, and an unlatched condition, permitting relative axial movement between the outer body and the inner body.